Clock gating is a technology used in a number of synchronizer circuits in order to reduce dynamic power loss.
An additional logic circuit is needed to supply or gate a clock signal. Since the additional logic circuit is capable of gating (or blocking) a clock signal supplied to a specific circuit when an operation of the specific circuit is not required, flip-flops included in the specific circuit do not switch a logic value and maintain an existing logic value when a clock signal is blocked. Switching a logic value of a flip-flop consumes power. When the logic value is not switched or changed, power consumption due to switching is zero and only power consumption due to leakage currents occurs. In general, since power is consumed in proportion to a frequency, the power consumption due to switching is zero when the frequency is zero.
Clock gating can be easily applied between the same clock domains. However, since a control signal for controlling clock gating included in one clock domain needs to be generated in another clock domain, complexity of an additional logic circuit for the clock gating is increased and the clock gating between the different, or heterogeneous, clock domains may be difficult to perform in some cases. The “same clock domains,” as that phrase if used herein, means domains that use clock signals having the same frequency. The phrase “different clock domains,” as that phrase is used herein, means the domains use clock signals that have different frequencies.
In some systems or device, such as in system on a chip (SOC), for example, multiple synchronizer circuits are often employed. Each of the synchronizer circuits consumes power, and the overall power consumed by all of the synchronizer circuits can reduce the battery lifetime of the device or system in which the synchronizer circuits are employed. Accordingly, a need exists for a synchronizer circuit that consumes a relatively low amount of power, thereby increasing the battery lifetime of the system or device in which the synchronizer circuit is employed.